I start all my JSP files with 

<%@ include file="/WEB-INF/common/taglibs.jsp" %>

in which I define all common JSP includes, and most importantly pageEncoding:

<%@ page language="java" pageEncoding="UTF-8" contentType="text/html;charset=utf-8" %> <%@ taglib prefix="spring" uri="http://www.springframework.org/tags" %>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
[...]

This has worked on and off, without me being able to determine what triggers if it works or not. It appears not to work for .tag files all the time, when I use a similar setup for .tag files:

<%@ include file="../include.tag" %>

include.tag:
<%@ tag body-content="empty" pageEncoding="UTF-8" language="java" %>
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags" %>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
[...]

This works perfectly when the file is deployed in eg tomcat 7/8, and in IntelliJ.

I just tested with current nightly (20150520), and it seems to work better.

Doesn't seem to work outside war type projects. Eg in a gradle project, you explicitly need the encoding header in every single JSP file.